96 MUSCULAR TISSUE 



ules of Kolliker), and glycogen granules. Fat granules, 'liposomes' 

 (Bell) of probably nutritive significance, and varying greatly in amount 

 according to the functional condition of the individual, are normally 

 present in cardiac muscle (J-lnllurd, Amer. Jour. Anat., 1-4, 1, 1912). 

 This fatty content can be demonstrated by the several mierochemical 

 technics for lipoids. According to Meves, Duesberg, and others, the myo- 

 fibrils of striped muscle differentiate from the mitochondria of the myo- 

 blasts; but since mitochondria can be demonstrated in highly developed 





FIG. 104. CARDIAC MUSCLE 'CELLS' FROM THE PIG'S HEART, ISOLATED IN 

 EQUAL PARTS OF ALCOHOL, GLYCERIN, AND WATER. 



Unstained. (The nuclei are somewhat darker than they actually appear.) X 410. 



fibers (Fig. 116) it seems improbable that mitochondria have anything 

 directly to do with the development of muscle fibrils. 



It has been claimed that heart muscle and striped muscle generally 

 can be interpreted in terms of muscle cells, and intercellular myofibrillae, 

 in analogy with connective tissue (Baldwin). But the presence of a con- 

 tinuous axial core of undifferentiated sarcoplasm, lack of a definite cell 

 membrane separating this sarcoplasm from the outlying myofibrillas, in- 

 ability to separate such 'cells' by dissociation methods, and the extension 

 of the telophragma to the nuclear wall, seem to render this view unten- 

 able. 



The myofibrils must be further considered. No distinction between 

 border fibrils and central fibrils, as in smooth muscle, is possible in car- 

 diac muscle. But the myofibrils undergo greater differentiation. This 



